Ignition Mixtures

ABSTRACT

A firing mixture which contains explosives, oxidizing and reducing agents is characterized in that it contains one or several explosives which can be fired by laser light. Also disclosed is a process for producing the same and its use.

[0001] The present invention relates to ignition mixtures and manufacture and use thereof.

[0002] Ignition mixtures and primers are used to ignite pyrotechnic mixtures or primers as well as propellant charges. The pyrotechnic mixtures or primers can represent the single charge or a booster charge or a gas-generating primer. Propellant charges and primers convert into primarily gaseous components which can be used to trigger rapid-acting processes such as acceleration of projectiles, driving in fastening materials, for example with the aid of bolt setters, or inflating air bags or triggering belt tighteners in vehicle safety. One variant is represented by the use of liquid primers instead of solid primers. These exploit the reaction of liquid fuel with oxidizers to generate gases.

[0003] Ignition mixtures are generally triggered mechanically so that they must be sensitive to the action of friction and impact. They generally consist of initial or primary explosives such as lead trinitroresorcinate or diazodinitrophenol, reducing agents such as metal powder, or oxidizers such as barium nitrate or zinc peroxide. Sensitizers such as tetrazene or friction agents such as powdered glass, which increase the sensitivity of the initial explosive materials, are also used. For electrically ignitable systems, the rapid-reacting initial explosives are primarily used. However, the high mechanical sensitivity of the components required for perfect function is a disadvantage when handling the raw materials and mixtures. Handling requires special safety measures. Other types of ignition such as ignition by heat or by coupling high-frequency electromagnetic waves do not solve this problem or are suitable only for highly specialized and sharply limited applications.

[0004] The goal of the present invention is to provide new ignition mixtures.

[0005] In a first embodiment of the invention, the problem is solved by ignition mixtures that can be ignited by laser light. The explosives contained in the ignition mixtures according to the invention can be primary or initial explosives, secondary explosives, or mixtures of these explosives. The primary or initial explosives that can be used may for example be lead trinitroresorcinate, diazodinitrophenol, tetrazene, or potassium dinitrobenzofuroxanate, or mixtures of these explosives. Appropriate secondary explosives are chosen from nitrocellulose, hexanitrostilbene, nitrided aromatic compounds, and/or nitrided aromatic compounds with a polymer structure such as polynitropolyphenylether or polynitropolyphenylenes, from specific heterocycles such as nitrotriazolone, from the derivatives of tetrazoles such as aminotetrazole, ditetrazole, or diaminoguanidine azotetrazole, and from hexagene or octagene. Secondary explosives derived from urea and its derivatives can also be used. Examples of these are the urea derivatives biuret, guanidine, nitroguanidine, guanidine nitrate, aminoguanidine, aminoguanidine nitrate, thiourea, triaminoguanidine nitrate, aminoguanidine hydrogen carbonate, azodicarboxylic acid diamide, tetrazene, semicarbazide nitrate, as well as urethanes, ureides such as barbituric acid, and their derivatives. These explosives can be used alone or in a mixture. According to the invention, secondary explosives are preferred, and nitrided aromatic compounds with a polymer structure, in particular polynitropolyphenylether and the polynitropolyphenylenes or mixtures of these secondary explosives are particularly preferred.

[0006] In addition to the explosives, the igniters according to the invention also contain oxidizers and reducing agents which are common per se. Binders, processing agents, and pressing agents can also be used.

[0007] Oxidizers that may be used can be the peroxides of alkali metals and alkaline earth metals, zinc peroxide, and the peroxodisulfates of the aforesaid elements and of ammonium, nitrates of alkali metals, and alkaline earth metals, in particular lithium, sodium, potassium, or strontium nitrate, as well as ammonium nitrate, oxohalogen compounds of alkali metals or alkaline earth metals or of ammonium, and particularly preferably potassium perchlorate or ammonium perchlorate. Sulfur is also suitable as an oxidizer. These oxidizers can be used alone or in a mixture.

[0008] The reducing agents used according to the invention are metals such as titanium, zirconium, aluminum, magnesium, and cerium in the finely powdered form. Alloys of these metals as well such as titanium/aluminum or cerium/magnesium can be used according to the invention. Other reducing agents are carbon or boron. These reducing agents can be used alone or in a mixture.

[0009] Compounds from the group of polyesters or polyurethanes can be used as binders. Compounds with binding properties that contribute to the heat of explosion and/or the oxygen balance, for example nitrocellulose or polynitropolyphenylene, can also be used as binders.

[0010] Processing agents and pressing agents can be substances which for example improve flowability such as Aerosil or substances which impede dust formation and improve slip or meterability, such as graphite or boron nitride.

[0011] For improved absorption of laser light, the ignition mixtures according to the invention can also be dyed or reacted with dye pigments. Heat stability can also be improved if necessary by adding stabilizers. Substances used to stabilize nitrocellulose can for example be used for this purpose.

[0012] In addition, combustion moderates that affect the rate of combustion can be added to the ignition mixtures according to the invention.

[0013] Substances or mixtures thereof able to affect combustion and combustion rate by heterogenous or homogenous catalysis are used as combustion moderates. Moderator that participate in the reaction in the form of heterogenous catalysis are metals, metal oxides, and/or metal carbonates and/or metal sulfides. The metals that can preferably be used are boron, silicon, copper, iron, titanium, zinc, or molybdenum. Calcium carbonate can also be used. Mixtures of these moderators can also be used.

[0014] Moderators that react in the form of homogenous catalysis are for example sulfur, copper resorcilates, or ferrocene and its derivatives. These moderators are evaporated by the temperatures produced by the reaction and can thus affect the reaction themselves or as secondary products.

[0015] For protection against environmental influences, the ignition mixtures according to the invention can also be treated with protective agents or be coated.

[0016] The ignition mixtures according to the invention have multiple potential uses. For example, they are used to ignite pyrotechnic mixtures or primers as well as propellant charges that trigger rapid processes such as acceleration of projectiles, driving in fastening materials, for example with the aid of bolt setters, or inflating air bags or triggering belt tighteners in vehicle safety.

[0017] The safety data on some of the ignition mixtures according to the invention are provided in Table 2. The data were derived by the methods of the Bundesanstalt für Materialprüfung [Federal Institute for Materials Testing]. By comparison to the primary explosive lead nitroresorcinate, sensitivity to friction and impact are significantly improved with the igniting agents according to the invention.

[0018] In estimating important parameters of the ignition mixtures according to the invention such as the energy released by the reaction (beat of explosion), pressure, explosion temperature, and reaction products produced at this temperature, an adiabatic reaction was calculated with a thermodynamic computer program for the ignition mixtures according to the invention at constant volume and a loading density of 0.1 g/cm³. Table 3 shows the most important data in the thermodynamic calculation. The ignition energy necessary for triggering a reaction was determined experimentally.

[0019] The examples below are intended to illustrate the invention without restricting it.

EXAMPLES 1 to 16

[0020] The ignition mixtures according to the invention were produced by methods known of themselves. The individual components were sifted through a sieve with a small mesh size of 0.2 mm as shown in Table 1 and mixed in a tumble mixer for 30 minutes. 200 mg portions of these mixtures were pressed into pellets with a diameter of 6 mm with a pressing force of 71 N/mm². The pellets so produced were ignited with a laser beam (wavelength 1,060 nm) with an energy of approximately 200 mJ and a pulse length of 2.5 ms. The ignition behavior is shown in Table 1 TABLE 1 Examples Components 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 KNO₃ 52.5 52.5 33.3 32.3 33.3 40 40 B 18.8 18.8 2.9 2.9 10 10 binder 3.7 3 7 NPE 25 45 44.7 44 5 44.1 66 7 64.8 66.7 64.8 25 50 PNP 25 100 66.7 50 25 ZnO₂ 50 49.8 49.8 49 33.3 32.3 Ti  5 4.9 4.9 4.9 graphite 0.5 1 2 black powder 75 75 ignition behavior +++ + + + + + + ++ + + + +++ +++ + + +++

[0021] TABLE 2 Ex. Condensate Pressure T Heat Percentage Ignition Specimen (atm) (K) (cal/g) (%/mol) Energy (mJ) NPE 1109 2932 686 0 ≈10 NPE/KNO₃ 907.4 3073.5 672 7.5 160 66.7/33.3 NPE/ZnO₂Ti 1198 4146 978 14.6 ≈200 45/50/5 black pow- 430 2290 −179 11.6 ≈200 der/NPE 75/25 AZM O 622 3265 615 52 ≈200 9531/NPE 75/25 NPE/KNO₃/B 843 3374 673 29 ≈90 50/40/10 NPE/ZnO₂ 1341 4044 1016 7 >200 66.7/33.3 NPE/ZnO₂/B 1194 3731 991 14 >200 64.8/32.3/2.9 NPE/KNO₃/B 1002 3382 752 2 ≈100 64.8/32.3/2.9 NC/KNO₃ 872 3282 883 11 no ignition 66.7/33.3 lead trinitrore- 683 3639 550 10 ≈5 sorcinate

[0022] TABLE 3 Friction Impact Detonation Point Explosive Sensitivity (N) Sensitivity (J) (° C.) lead trinitroresor- 2 ≦0.025 280 cinate AZM O 2956 ≧360 5 >400 AZM O 9531 ≧360 4 >400 black powder ≧360 5 >400 HITP ≧360 15-50 >400 (aminotetrazole base) NPE ≧360 7.5 >260 NPE/ZnO₂/Ti ≧360 15 230 NPE/ZnO₂ 240 20 235 NPE/KNO₃ + 3% 160 4 decomposition B starting at 230 PNP/KNO₃ ≧360 10 293 PNP/KNO₃/B ≧360 10 293 

1. Ignition mixture containing explosives, oxidizers, and reducers, characterized in that it contains one or more explosive(s) that is/are ignitable by laser light.
 2. Ignition mixture according to claim 1 , characterized in that the explosive, alone or as a mixture, is selected from the primary or initial explosives, for example from lead trinitroresorcinate, diazodinitrophenol, tetrazene, or potassium dinitrobenzofuroxanate, or mixtures of these explosives.
 3. Ignition mixture according to claim 1 or 2 , characterized in that the explosive, alone or as a mixture, is selected from the secondary explosives, for example from nitrocellulose, hexanitrostilbene, from certain heterocycles such as nitrotriazolone, from the derivatives of tetrazoles such as aminotetrazole, ditetrazole, or diaminoguanidine azotetrazole, and from hexagene or octagene, from secondary explosives derived from urea and its derivatives such as biuret, guanidine, nitroguanidine, guanidine nitrate, aminoguanidine, aminoguanidine nitrate, thiourea, triaminoguanidine nitrate, aminoguanidine hydrogen carbonate, azodicarboxylic acid diamide, tetrazene, semicarbazide nitrate, from the urethanes, from the ureides such as barbituric acid and its derivatives, from nitrided aromatic compounds, or from nitrided aromatic compounds with a polymer structure such as polynitropolyphenolether or the polynitropolyphenylenes, or from mixtures of these explosives.
 4. Ignition mixture according to claim 3 , characterized in that the secondary explosive is chosen from nitrided aromatic compounds with a polymer structure.
 5. Ignition mixture according to one of claims 3 or 4, characterized in that the secondary explosive is chosen from the polynitropolyphenylethers and/or polynitropolyphenylenes.
 6. Ignition mixture according to one or more of claims 1 to 5 , characterized in that the oxidant is chosen from sulfur, the peroxides of alkali metals or alkaline earth metals, from zinc peroxide, from the peroxodisulfates of the aforesaid elements, and of ammonium, from the nitrates of the alkali metals and alkaline earth metals, in particular from lithium, sodium, potassium, or strontium nitrate as well as ammonium nitrate, from the oxohalogen compounds of alkali metals or alkaline earth metals or of ammonium, in particular from potassium perchlorate or ammonium perchlorate, or from mixtures of the aforesaid substances.
 7. Ignition mixture according to one or more of claims 1 to 6 , characterized in that the reducing agent is a metal, chosen from titanium, zirconium, aluminum, magnesium, or cerium, a mixture of these metals, an alloy of these metals such as titanium/aluminum, or cerium/magnesium, in that it is carbon or boron, or in that it is a mixture of the aforesaid substances.
 8. Ignition mixture according to one of more of claims 1 to 7 , characterized in that, in addition to the explosives, oxidizers, and reducing agents, it contains binders and/or processing agents and/or pressing agents and/or combustion moderators known of themselves.
 9. Ignition mixture according to one or more of claims 1 to 8 , characterized in that it is dyed or reacted with dye pigments.
 10. Ignition mixture according to one or more of claims 1 to 9 , characterized in that substances or mixtures thereof are used as combustion moderators that are appropriate for affecting combustion and the rate thereof by heterogeneous or homogenous catalysis.
 11. Method for manufacturing the ignition mixture according to one or more of claims 1 to 10 , characterized in that the individual components are mixed then pressed.
 12. Use of the ignition mixture according to one or more of claims 1 to 10 for igniting pyrotechnic mixtures or primers as well as propellant charges.
 13. Ignition mixture according to one or more of claims 1 to 10 , characterized in that it contains a mixture of primary and secondary explosives. 